Cathode-ray tube scanning apparatus



July 5, 1960 A. HAZELTINE 2,944,173

CATHODE-RAY TUBE SCANNING APPARATUS Filed July 17, 1958 2 Sheets-Sheet 115, I A. HAZELTINE 2,944,173

I CATHODE-RAY TUBE scmmmc APPARATUS Filed July 17, 1958 z Sheets-Sheet 2I I I l I I I I I I I l I I I I I I FIG. 4 I I I l I l I I I I I I l l II l I J I I v I 23 I l I E I l z l 5E o I I I |ao I360 0 I I 2 a 20 30 zI ANGULAR DISTANCE FIG.5

United States Patent ice CATHODE-RAY TUBE SCANNING APPARATUS AlanHazeltlne, Maplewood, N.J., assignor to Hazeltine Research, Inc.,Chicago, 111., a corporation of Illinois Filed July 17, 1958, Ser. No.749,275

4 Claims. (Cl. 313-77) flection in one direction and which enables theuse of deflection circuit components with lower power ratings.

In supplying scanning currents to the horizontal and vertical deflectionyoke windings of a cathode-ray tube, it is sometimes found to be morediflicult to secure suflicient power for producing deflection in onedirection than for producing deflection in the other. This isparticularly true in television receiver systems where approximately tentimes as much power is required to produce horizontal deflection ascompared to that necessary to produce vertical deflection. This increasein power is required due to increased losses occurring at the higherhorizontal scanning frequencies. It is a serious problem even whenvacuum tube deflection circuits are utilized. In the case of vacuum tubecircuits the problem is overcome by using components with suitably highpower ratings. However, in some applications such as transistortelevision receivers,

it becomes important to provide some solution tof this problem whichwill allow the use of circuit components which are smaller in size andthereforeh-ave lower power ratings. p i p An early solution is to befound inUnited States Patent 2,177,688, issued to MadisonCawein onOctober 31,

1939, wherein there is disclosed an arrangement or" permanent magnetslocated around and abutting the neck of a television tube between thedeflecting yoke and the tube bell for augmenting the horizontaldeflection. However, such an arrangement is difficult to apply tocathode-ray tubes favored in present-day practice, especially thosefound in portable receivers, since the tracks of such tubes are shortand the available space around them is fully occupied by the yokewindings, the magnetic core around these windings, the ion trap, andperhaps the focusing and centering arrangements. Moreover, this magneticcore would tend to short-circuit the magnetic field of permanent magnetsplaced close to it. Furthermore, it is ditficult to arrange permanentmagnets in such a way as to to prevent their field from producing acertain amount of undesirable picture. distortion. I i It is an objectof the present invention to provide new and improved scanning apparatusto augment the electron-beam deflection and which avoids thedisadvantages of prior such apparatus.

It is another object of the present invention to provide scanningapparatus which produces a constant magnetic field so distributed acrossthe cross-section of the electron beam that substantially no distortionof the picture results.

It is a further object of the present invention to provide scanningapparatus which may be utilized in conjunction with small short-necked,wide deflection angle cathoderay tubes without substantially increasingthe size of such apparatus. 1

In accordance with the present invention, cathode-ray Patented July 5,1960 tube scanning apparatus for providing augmented beam deflectioncomprises deflection winding means for scanning the beam, magnetic coremeans encompassing the deflection means, means for supplying a directcurrent and means including a four-pole auxiliary winding responsive tothe direct-current supply means and disposed between the core means andthe tube for providing a uniformly changing magnetic field across thebeam-deflection area. In one form of the invention the auxiliary windinghas its longitudinal sides distributed substantially sinusoidally aboutthe tube. In another form, the sides are distributed uniformly throughfour angular regions about the tube. a

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription taken in connection with'the accompanying drawings, and itsscope will be pointed out in the appended claims.

Referring to the drawings:

Fig. 1 is a diagrammatic cross-sectional side view of a portion of acathode-ray tube showing a preferred embodiment of the presentinvention;

Fig. 2 is a diagrammatic cross-sectional view through the neckof thecathode-ray tube of Fig. 1;

Fig. 3 shows components of magnetic intensity produced by the auxiliarywinding;

Fig. 4 shows diagrammatically the manner in which the auxiliary windingis wound, and

Fig. 5 is a graph of magnetic potential over the inner surface of theauxiliary winding of Fig. 2 plotted against the angular distance aroundthe circumference.

Referring to Figs. 1 and 2 there is shown cathode-ray tube scanningapparatus for providingaugmented beam deflection which comprises in partdeflection winding windings might alternatively be of the saddleyokeconstruction described at pages 610 of Television Engineering Handbook,edited by Donald G. Fink, McGraw-Hill Book 'Co., Incl, 1957. Thesewindings are preferably placed directly over the glass neck of the tube10.

The cathode-ray tube scanning apparatus further comprises a magneticcore means encompassing the deflection means. As shown in Fig.2 themagnetic core 13 sur rounds the horizontal andvertical deflectionwindings 11, 11 and 12, 12 and auxiliary winding 15, in accordance withthe present invention. The windin g 15 is more fully describedhereinafter. The core serves" as a return path for the magnetic flux ofall three windings.

In addition to the conventional deflection windings and themagnetic'core, the apparatus further comprises means for supplying adirect current and means including a four-pole auxiliary windingresponsive to the directcurrent supply means and disposed between thecore means and thetube for providing a uniformly changing magnetic fieldacross the beam deflection area. In one form of the invention theauxiliary winding has its longitudinal sides distributed substantiallysinusoidally about the tube. In another form the auxiliary winding issymmetrical and has its longitudinal sides distributed uniformly throughfour angular regions being substantially equal to 60. These meansinclude in Figs. 1 and 2 the direct-current voltage supply 16 and theauxiliary winding 15, which is a single layer winding disposed betweenthe magnetic core 13 and the horizontal and vertical defleconly in theflat portion of the deflection windings, are

the axis.

current of the auxiliary winding. .lscribed, for the ideal condition.of. no distortion, the sides iof the coils comprising thelwindingarehhbstantially sinusoidally distributed about the neck of the tube. In

preferably wound to conform to the configuration of the deflectionwindings. In winding the auxiliary winding the four coils comprising thewinding are spirally wound in reverse sequence and serially connected sothat the adjacent sides of any two neighboring coils produce a magneticfield in the same relative direction.

Referring to Fig. 4, the auxiliary winding is shown in 7 developed form,namely, before being wrapped around the neck of the cathode-ray tube 10.The winding comprises four coils 18, 19, 20, and 21, each coil havingthe conductors in its longitudinal side preferably parallel andstraight. For the case of sinusoidal distribution of the coil sides thedensest portions of the windings are arranged at the horizontal andvertical axes relative to the desired direction of increased beamdeflection. The direction of direct-current flow through the windingthen determines the axis of increased beam deflection. For reasons to beexplained hereinafter, it may be more practical to wind the coilswithout adhering to the rigorous sinusoidal distribution. In Fig. 4, onesuch preferred form of a winding is shown wherein each longitudinal coilside has a width which covers an angular distance of on therebyproducing an angular distance of 20: when adjacent coils are placed inabutting relation. The angle, a, is preferably substantially equal to30. When wound in this fashion the magnetic pole, which is the center ofthe coil, has a width equal to the width of one longitudinal side of thecoil.

In describing the operation of the apparatus, reference is made to Fig.3 wherein the ideal magnetic field, developed by a sinusoidaldistribution of coil sides of the auxiliary winding 15, is shown ashaving a vertical component intensity H directly proportional to thehorizontal distance x from the longitudinal axis 17 of the tube 19 andreversing in direction with a reversal in x. In a television receiver inwhich it is desired to augment the horizontal deflection, the x axiswould lie along the horizontal plane and would preferably orthogonallyintersect the axis-of-rotation 17 of the tube 10. The linearly increasing magnetic field increases the horizontal deflection by aconstant factor. While the vertical component H is produced there isunavoidably present, at the same time, the horizontal componentintensity I-I which ideally isrdirectly proportional to the verticaldistance y from Such a field will then decrease the vertical deflectionby a constant factor in the same manner in which the horizontaldeflection was increased. Thus, less power is required of the horizontaldeflection wind ings 11, 11 and correspondingly more power is requiredof the vertical deflection windings 12, 12.

Due to the ideal uniformly changing field developed, the picture isnot'distorted. By uniformly changing is meant linear variation withrespect to distance from the ,tube axis. The reason for this lack ofdistortion can be where r and 0 are the polar coordinates of any pointwithin the field and distant from its ends. With a symmetrical fourpolefield the solution of this equation becomes; I

r r 1 V=a sin 26+ a sin 66+c sin 106+ .where R is the inner radius ofthe auxiliary winding and the as are constants determined by, thedistribution and As previously de- 25. this case all the as of Equation2 are at zero except a;, in which case the equation simplifies to:

r r V= or S111 20=2a sin 0 cos 0 Thus H is independent of x and directlyproportional to y. H is independent of y and directly proportional to x.These are the desired relations illustrated in Fig. 3. The correspondingadditional deflections d and d are indicated by the dotted arrows, thecurrent of the auxiliary winding having such direction as to increasehorizontal deflections at the expense of decreased vertical deflections.

In place of a sinusoidal distribution, it may be more convenient to usean auxiliary symmetrical windinguniformly distributed over portions ofthe circumference, as illustrated in Fig. 2. The magnetic potential justinside the auxiliary winding (r=R) is then as represented in Fig. Sandas expressed by the Fourier series:

V= k sin 2a sin 28+ sin 60: sin 69 Sin Sn; 100+ sin 6na= sin n=0 (n=1,3, s, (6)

Equation 5 then reduces to sin 220+ At any point r, 0 in the field, themagnetic potentiahby 1 l sin 146 112 Equation 2, is then V=k sin 60 R2S111 To obtain an estimate of the distortion due to the departure ofthis magnetic potential from the ideal sinusoidal distribution, theradial and tangential components of magnetic intensity may be found fromEquation 8:

th k sin 60- Z sin 20 Using the maximum values 1 of the sines andcosines, the values of the second terms relative to the first are eachequal to 1 l i 5 R 5-2 l280 at a radial distance r==R/2 within whichpractically all of the electrons of the beam will be confined. Thisvalue, 1/1280, is so small that the departure from the ideal conditionis unimportant; and the values for higher terms are smaller still. Sodistortion due to the departure of V in Fig. 5 from the ideal sinusoidaldistribution is quite tolerable with a=30.

When used in conjunction with a television-receiver scanning system theauxiliary winding need comprise merely a single layer. Since the voltageof this winding is low it requires no insulation other than the ordinarytype of wire insulation.

It can be seen that the desired increase in beam deflection and asimultaneous decrease in component power rating may be produced by thepresent invention without occupying space about the tube alreadynecessary for conventional image-reproducing apparatus. Since only asingle layer, lightly insulated winding is necessary to practice thisinvention, the very small extra space required may be provided byslightly increasing the diameter oi the magnetic core 13 oralternatively by decreasing the size of windings 11, 11 and 12, 12 orboth.

While there has been described what is at present considered to be thepreferred embodiment of this invention, it Will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed to cover all such changes and modifications as fall within thetrue spirit and scope of the invention.

What is claimed is:

1. Cathode-ray tube scanning apparatus for providing augmented beamdeflection, comprising: deflection winding means for scanning the beam;magnetic core means encompassing the deflection means; means forsupplying a direct current; and means including a four-pole auxiliarywinding responsive to the direct-current supply means and disposedbetween the core means and the tube for providing a uniformly changingmagnetic field across the beam-deflection area, said auxiliary windinghaving its longitudinal sides distributed substantially sinusoidallyabout the tube.

2. Cathode-ray tube scanning apparatus for providing augmented beamdeflection, comprising: deflection Winding means for scanning the beam;magnetic core means encompassing the deflection means; means forsupplying a direct current; and means including a four-pole auxiliarywinding responsive to the direct-current supply means and disposedbetween the core means and the deflection means for providing auniformly changing magnetic field across the beam-deflection area, saidauxiliary Winding having its longitudinal sides distributedsubstantially sinusoidally about the tube.

3. Cathode-ray tube scanning apparatus for providing augmented beamdeflection, comprising: deflection winding means for scanning the beam;magnetic core means encompassing the deflection means; means forsupplying a direct current; and means including a fourpole symmetricalauxiliary winding responsive to the direct-current supply means anddisposed between the core means and the tube for providing a uniformlychanging magnetic field across the beam-deflection area, said auxiliarywinding having its longitudinal sides distributed through four angularregions about the tube, said regions being substantially equal to 4.Cathode-ray tube scanning apparatus for providing augmented beamdeflection, comprising: deflection winding means for scanning the beam;magnetic core means encompassing the deflection means; means forsupplying a direct current; and means including a four-pole symmetricalauxiliary Winding responsive to the direct-current supply means anddisposed between the core means and the deflection means for providing auniformly changing magnetic field across the beam-deflection area, saidauxiliary winding having its longitudinal sides distributed through fourangular regions about the tube, said regions being substantially equalto 60.

References Cited in the file of this patent UNITED STATES PATENTS2,177,688 Cawein Oct. 31, 1939 2,414,925 Buckbee Jan. 28, 1947 2,455,977Bocciarelli Dec. 14, 1948 2,467,009 Bull et al. Apr. 12, 1949 2,498,354Bocciarelii Feb. 21, 1950 2,578,343 Ekvall Dec. 11, 1951 2,846,606 Joneset al. Aug. 5, 1958 2,855,530 Hamann Oct. 7, 1958 FOREIGN PATENTS739,068 Great Britain Oct. 26, 1955

